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// Directory & authentication

Port 5635: SFM Authentication Subsystem

Port 5635 is assigned by IANA to sfmsso (SFM Authentication Subsystem).

5635

How sfmsso works

Directory & authentication
userdirectorysfmssoresponse userdirectorysfmssoresponse

The client proves who it is on port 5635 and gets an answer (or a ticket) it can use with other services.

Transport
TCP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Directory & authentication
01 Security

Is port 5635 dangerous?

We have no specific security note for port 5635. Its risk depends on the program actually listening on it. General advice for directory & authentication services:

  • Keep directory and authentication services on internal networks.
  • Require signing or TLS and disable anonymous queries.
  • Monitor authentication failures for spraying and brute force.
02 Registry

IANA registry entries for port 5635

ServicePortTransportDescriptionReferenceUpdated
sfmsso 5635 TCP SFM Authentication Subsystem - 2008-09-15
-5635-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 5635, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5635'      # process listening on 5635
sudo lsof -nP -i :5635

macOS

sudo lsof -nP -i :5635

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5635 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5635
netstat -ano | findstr :5635

From another machine

nmap -p 5635 -sV <host>
nc -zv <host> 5635

Block it in the firewall

sudo ufw deny 5635/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5635" -Direction Inbound -LocalPort 5635 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5635 used for?

Port 5635 is assigned by IANA to sfmsso (SFM Authentication Subsystem).

Is port 5635 TCP or UDP?

Port 5635 is registered for TCP.

Is it safe to open port 5635?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Keep directory and authentication services on internal networks.

How do I check if port 5635 is open?

On Linux run "ss -ltnup 'sport = :5635'", on macOS "lsof -nP -i :5635", and on Windows "netstat -ano | findstr :5635" to see the local process. From another machine, "nmap -p 5635 <host>" shows whether it is reachable.

05 Related
:389 LDAP tcp · udp · high risk :636 LDAPS tcp · udp · moderate risk :88 Kerberos tcp · udp · high risk :3268 Global Catalog (LDAP) tcp · udp · high risk :1812 RADIUS udp · tcp · moderate risk :31 MSG Authentication tcp · udp :49 Login Host Protocol (TACACS) tcp · udp :56 XNS Authentication tcp · udp

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